Feedback Resource Mapping in Wireless Communications

ABSTRACT

A feedback radio resource in a license-exempt frequency band maps from a data radio resource to at least one frequency sub-band which the data resource excludes. The feedback resource is also spaced in time from the data resource by a predetermined interval. Feedback (ACK/NACK) for data received in the data resource is then sent in the feedback resource. In various embodiments the sub-band is one or more edges of the data resource channel, or of a license-exempt component carrier. The predetermined interval may be a function of how much of the data resource is occupied by data. The data transmitting device delays sending its data by a time offset from the end of a previous transmission on that channel, or if it does not know the end time it delays until the predetermined interval plus the length of the feedback resource have lapsed. Various synchronization aspects are also disclosed.

CROSS REFERENCE TO RELATED APPLICATION

This application claims benefit under 35 U.S.C. §119(a) and 37 CFR 1.55to UK Patent Application 1119864.5, filed on Nov. 17, 2011.

TECHNICAL FIELD

The exemplary and non-limiting embodiments of this invention relategenerally to wireless communication systems, methods, devices andcomputer programs and, more specifically, relate to radio resources forfeedback signaling such as for acknowledgements and negativeacknowledgements.

BACKGROUND

The following abbreviations that may be found in the specificationand/or the drawing figures are defined as follows:

3GPP third generation partnership project

ACK acknowledgement

eNB evolved NodeB (BS of a LTE/LTE-A system)

FDD frequency division duplexing

HARQ hybrid automatic repeat request

LTE long term evolution (evolved UTRAN)

LTE-A long term evolution advanced

NACK negative acknowledgement

PSS primary synchronization signal

RAT radio access technology

RF radiofrequency

SSS secondary synchronization signal

TDD time division duplexing

TX transmission

UE user equipment

UTRAN universal terrestrial radio access network

WLAN wireless local area network (sometime termed WiFi)

Wireless radio operations in licensed frequency bands has been utilizedto such an increasing extent that portions of the radio spectrum thatstill remain available have become limited. Various network operators,service providers, communication device manufacturers, and communicationsystem manufacturers are therefore seeking efficient solutions toutilize unlicensed frequency bands, also termed shared band or bands andmore formally as license-exempt bands. Communication on an unlicensedshared band is generally based on sharing an available channel betweendifferent communication devices. The different communication devices mayutilize a common RAT, but in certain scenarios the differentcommunication devices may utilize different RATs.

In an unlicensed shared band the channel access can be distributed, inwhich the communication devices detect a channel and utilize a channelreservation scheme known to other communication devices in order toreserve a right to access the channel. In distributed channel access, atransmitting communication device and a receiving communication deviceare generally not synchronized to a global reference. Transmissions onan unlicensed shared band that do not utilize a common timing reference(one shared by both the transmitting communication device and thereceiving communication device) are generally short in duration in orderto allow multiple communication devices to share the channel. Generally,in this scenario a transmitting communication device only transmits afew packets at a time before the transmitting communication devicedefers its access to some other transmitting communication device thatalso occupies the channel. After a random duration, the firsttransmitting communication device then transmits again. Thereforespecific measures are required in order to initially synchronize thetransmitting communication device and receiving communication device atthe beginning of each data transmission. This is sometimes done bysynchronizing the receiving communication device with the datatransmission (that is, informing the receiving communication device whenthe first packet of the data transmission begins).

In addition to synchronization, the transmitting communication devicecan indicate frequency resources that can be utilized for transmission.In general a transmitting communication device may only utilize aportion of the frequency resources, and can indicate to the receivingcommunication device which portion of the frequency resources thetransmitting communication device will utilize for transmission. In oneprior art technique for communicating in the license-exempt band, atransmitter sends at least two synchronization sequences having cyclicshift characteristics prior to the data transmission. The intent is thatthe first sequence is used to synchronize the receiver and the cyclicshift in the subsequent sequence(s) is/are used to inform the receiverabout the radio resources being used for the data transmission. Theresource mapping between the cyclic shift that the receiver observes andactual radio resources used by the transmitter can be implemented usinga tree-based method such as that shown at FIG. 1. The unlicensedbandwidth is divided into predetermined channels and the transmittedcyclic shift maps to a specific radio resource or resources on aspecific channel. Those teachings are not seen to provide an efficientmanner for organizing feedback from the receiver to the transmitter,such as ACK and NACK messages.

The WLAN family of standards (IEEE 802.x) transmit MAC level feedback onthe same resource as the actual data transmission after a shortinterframe space SIFS period (10 us). This is not seen to be efficientfor broader implementation since the feedback thereby requires the wholebandwidth used by the WLAN for transmitting the original data. The LTEsystem conveys its uplink hybrid automatic repeat request HARQ ACK/NACKfeedback for a dynamically scheduled downlink data transmission on aphysical uplink control channel PUCCH channel which is derived from thephysical downlink shared channel PDSCH on which the data was sent. Oralternatively if there is an uplink resource allocated for the time thefeedback is to be sent the LTE system multiplexes the feedback with thatuplink data sent on the allocated physical uplink shared channel PUSCH.

While there are many proposals for exactly how communications in theunlicensed band should be managed among the various devices seekingaccess, operation in the unlicensed shared band generally involvessharing one or more channels in a communication system between one ormore communication devices, where the communication devices can utilizedifferent RATs. What is needed is a way to provide effectiveasynchronous/contention-based access over a shared band with dynamic andscalable spectrum allocation. This is not only for expanding theavailable spectrum over which user devices may communicate but also tosupport ad hoc networked wireless mobile robotics which currentlyoperate primarily using IEEE standards such as 802.11 and 802.15.4.These teachings provide a feedback mechanism which may be advantageouslyused in the unlicensed band, and which is scalable and dynamic withminimal added control signaling.

SUMMARY

The foregoing and other problems are overcome, and other advantages arerealized, by the use of the exemplary embodiments of this invention.

In a first exemplary embodiment of the invention there is an apparatuscomprising at least one processor and at least one memory storing acomputer program. In this embodiment the at least one memory with thecomputer program is configured with the at least one processor to causethe apparatus to at least: map a feedback radio resource in alicense-exempt frequency band from a data radio resource to at least onefrequency sub-band which the data radio resource excludes and spaced intime from the data radio resource by a predetermined interval; and sendor receive feedback for information received or sent on the data radioresource on the mapped feedback radio resource.

In a second exemplary embodiment of the invention there is a methodcomprising: mapping a feedback radio resource in a license-exemptfrequency band from a data radio resource to at least one frequencysub-band which the data radio resource excludes and spaced in time fromthe data radio resource by a predetermined interval; and sending orreceiving feedback for information received or sent on the data radioresource on the mapped feedback radio resource.

In a third exemplary embodiment of the invention there is a computerreadable memory tangibly storing a computer program executable by atleast one processor, the computer program comprising: code for mapping afeedback radio resource in a license-exempt frequency band from a dataradio resource to at least one frequency sub-band which the data radioresource excludes and spaced in time from the data radio resource by apredetermined interval; and code for sending or receiving feedback forinformation received or sent on the data radio resource on the mappedfeedback radio resource.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a prior art diagram of a tree-based mapping between radioresources and cyclic shifts for synchronizing a transmitter with areceiver for communication in the unlicensed band.

FIG. 2 is a schematic diagram illustrating component carriers in awireless radio access technology which utilizes carrier aggregation.

FIG. 3 is a time versus frequency diagram of channels and signalingaccording to an exemplary embodiment of these teachings.

FIG. 4 is a logic flow diagram that illustrates from the perspective ofthe communicating devices the operation of a method, and a result ofexecution of computer program instructions embodied on a computerreadable memory, in accordance with an exemplary embodiment of theseteachings.

FIG. 5 is a simplified block diagram of two communicating devices/userequipments, each operating under a different radio access technology intheir respective licensed bands and communicating directly with oneanother on a license-exempt band, which are exemplary electronic devicessuitable for use in practicing the exemplary embodiments of thisinvention.

DETAILED DESCRIPTION

Embodiments of these teachings are advantageously practiced in thelicense-exempt band, which in the United States includes televisionwhitespaces which the Federal Communication Commission is consideringopening for user communications, and which also include the industrial,scientific and medical (ISM) band which has traditionally been availablefor such communications at low power. In current understanding there isto be a database of available whitespace channels which certain nodes,whether network access points or the portable devices themselves, canaccess and update. These channels are identified by an index number andthere may be wireless signaling to inform some portable devices of theavailable channels in case those portable devices lack the ability toaccess the database themselves.

The LTE system deploys its total bandwidth as multiple componentcarriers, of which FIG. 2 is an example. Each user in the licensed bandis assigned a primary component carrier (PCell) and may be assigned alsoone or more secondary component carriers (SCell). There are various waysto deploy these component carriers: one or more may be backwardscompatible with LTE Release 8 while others may not be due to a lack ofsome or all control channels or a bandwidth not fitted to the 20 MHzstructure of Release 8; different component carriers may have differentbandwidths; some or all may not be frequency-adjacent to the others; andone or more may lie in license-exempt bands. SCell #3 illustrates such alicense-exempt component carrier. Carrier aggregation is not limitedonly to LTE.

According to an exemplary embodiment of these teachings there is bothsignaling of data on a first radio resource and feedback relevant forthat data on a second radio resource. For convenience and without lossof generality, the first radio resource is termed herein as a data radioresource and the second radio resource is termed herein as a feedbackradio resource. The examples below present two devices in communicationwith one another though more than two devices may be engaging in acommon (clustered) communication. The device transmitting the data andreceiving the feedback is termed the first device and the devicereceiving the data and transmitting the feedback is termed the seconddevice. These examples also mention a third device which is not part ofthe communications ongoing between the first and second device but whichis also using the license-exempt band, and so the examples describe howthe first and second devices avoid interfering with that third device(and vice versa).

FIG. 3 is a time (horizontal) and frequency (vertical) diagram ofcertain channels and radio resources which illustrate one particularembodiment for implementing the invention described herein. In onenon-limiting embodiment the data resource is found as follows. There isa common channel 302 (which may or may not lie in the license-exemptband) of which the various communicating devices are aware. A primarysynchronization signal PSS 304 is transmitted on that common channel302, such as on centrally-disposed orthogonal frequency divisionmultiple access OFDMA subcarriers mapped about a center frequency ofthat common channel. The first device transmits the PSS 304 with acyclic shift which maps to the data radio resource (or multiple cyclicshifts which map to it). FIG. 3 illustrates two PSSs 304 each with acyclic shift that maps to a different data radio resource 306-0, 306-1each on a different channel 0 and 1. Other embodiments of theseteachings may signal the data radio resource to the second device inother manners such as explicitly on the common channel at times whichavoid the PSS which may be sent at pre-determined intervals.

The second device is routinely monitoring the common channel 302 and sofrom reading the PSS 304 it knows where to find the data sent to it bythe first device. Both the first and second devices map from the dataradio resource to the feedback radio resource as follows, the firstdevice in order to know where to find the feedback it expects to receiveand the second device to know where to send that feedback. The feedbackradio resource is spaced in time a pre-determined time interval 308(which FIG. 3 shows in channel 5 but for this example is used onchannels 0 and 1 for the mapping) from the data radio resource 306-0 onchannel 0 to the feedback resource 310-0 on channel 0 (and similarly onchannel 1 for resources 306-1 and 310-1). And the feedback radioresource 310-0, 310-1 is in at least one frequency sub-band which theradio resource 306-0, 306-1 from which it maps excludes. At FIG. 3 suchexcluded sub-bands (for example, OFDMA subcarriers) are at both edges ofthe channel in which lie the data radio resource 306-0, 306-1. Noteparticularly that the data radio resources 306-0 and 306-1 do not occupythe entire frequency bounds of their respective channel.

In another embodiment the feedback radio resources lie at both frequencyedges of the license-exempt component carrier rather than edges of theindividual channel as FIG. 3 illustrates. In this embodiment, assumingthe whole license-exempt component carrier were divided into only theseven channels illustrated at FIG. 3 (numbered channels 0, 1, . . . 6),then the feedback resources would lie along the upper edge of channel 0(as shown for the feedback radio resource 310-0) and/or along thelowermost edge of channel 6. In contrast to the implicit mapping used inthe LTE system, in this embodiment the feedback resources are derivedfrom the cyclic shift used for resource allocation with the certain timedelay after the end of the data transmission in the data radio resource.In any of these embodiments the feedback resource may be at one but notboth edges though FIG. 3 illustrates it lying at both edges of therespective channel.

Returning to the example illustrated at FIG. 3, the feedback radioresources 310-0, 310-1 thereby lie at the outer edge of each channelused in an aggregated resource allocation by the transmitter, after thepredetermined interval 308. In an embodiment that predetermined intervalis based on a certain processing delay needed by the second device toreceive and decode the data in the data radio resource. During thisinterval 308 a third device can use the same channel for transmittingdata, shown at resources 326-0, 326-1, 326-2 and 326-4 which map fromthat third device's PSS and cyclic shift 324 on the common channel 302.This is unlike WLAN specifications which reserve the whole channel fromthe onset of the data resource to the end of the feedback resource forthe data and feedback between the first and second devices. In theembodiment shown at FIG. 3 two of the data radio resources 326-0, 326-1which the third devices utilizes for its data overlap in time with thefeedback radio resources 310-0 utilized by the second device to send itsACK/NACK for the data at resources 306-0 (and 306-1) to the firstdevice.

In a specific embodiment the processing delay, and therefore theinterval 308, is a function of the how much of the data radio resource306-0 is actually used for the first device's data. While the timeperiod is not fixed it is predetermined based on the data volume in thedata radio resource 308-0 (or said another way, based on the time fromthe start to the end of the data transmitted in the data radioresource). Defining the interval 308 in this way rather than as a fixedtime period regardless of how much of the resource 306-0 was used allowsa lower HARQ round trip delay for smaller bandwidth transmissions viathis dynamic feedback delay setting.

In a preferred embodiment the third device will have listened onchannels 0 and 1 which it later schedules by its own PSS 324, andhearing the data there the third device will consider where the mappedfeedback resources 310-0, 310-1 will lie so the third device cansynchronize its data transmissions at 326-0, 326-1, 326-1 and 326-4 onthe symbol level. This helps preserve orthogonality between the datasent by the third device (at 326-0, 326-1) and the feedback sent by thesecond device (at 310-0, 310-1) on the same channel (channels 0 and 1 inFIG. 3). Additionally it helps propagate a common synchronization in thelicense-exempt band so that radio resources may be more efficiently usedsystem-wide.

Now consider if the third device was not synchronized with the first andsecond devices. If we assume there is no guard band to keep thetransmissions 326-0 and 310-0 separate in time (since such a guard bandwould be quite spectrum-inefficient for the license-exempt band), thenthere is the problem of a non-orthogonality condition among subcarriersof a channel used simultaneously for feedback 310-0 and data 326-0transmissions, and vice versa. Embodiments of these teachings alleviatethis problem in two ways, depending on whether the third device is awareor not of when the transmission from the first device has ended. If thethird device is aware of the end time of the first device's datatransmission (the data transmission in data resource 306-0 in channel 0of FIG. 3), then there is defined a time offset 330 from the end of thedata transmission 306-0 on a channel to the beginning of the new datatransmission on the same channel by any device, and this offset 330 isan integer multiple of the symbol time used in the system. Even if notsynchronized with one another, each device will know the symbolstructure used in the system and so will know the symbol time, but ifnot synchronized the symbol edges from different devices will not align.

If instead the third device is not aware of the end time of the firstdevice's transmission on a given channel, then the third device willdelay its own transmission by a time amount larger than the fixed timedefined between the end of the data transmission and the correspondingfeedback transmission (the interval 308) plus the time length of thefeedback radio resource 309 which is fixed since the feedback is only anACK or a NACK or possibly also/or a channel quality indictor. This isshown at channel 5 of FIG. 3, the result being that no other devicewhich is unaware of the end time t1 of that data resource 350-5 willtransmit until time t2 when the feedback resource 360-5 is passed.

In the above two examples for imposing a delay it was described that thevarious devices will delay their data transmissions. While true, in thespecific FIG. 3 embodiment for scheduling the data radio resource thisdelay is implemented by delaying the start of the device's data radioresource which follows from the cyclic shift they send in their PSS onthe common channel 302.

Above it was mentioned that it is advantageous if the samesynchronization was propagated through the system so all devices on theunlicensed band would have the same timing. To that end embodiments ofthese teachings define a distributed synchronization propagation inwhich each device follows the synchronization of the last detected PSSsignals of any other device on the common channel, provided that thetime elapsed from the detection of that last PSS is not larger than acertain synchronization expiration timer running in the device. Theeffect of this embodiment is that when transmitting PSS signalsaccording to timing detected from previous PSS signals, the transmittingdevice propagates the synchronization further for other deviceslistening on the common channel 302. The new transmission of PSS signalsshall happen in integer multiples of symbol time of the system after anearlier detected PSS signal transmission. If instead the transmittingdevice has not detected any PSS signals within that certain time period(the timer expiration period) then it can send its own PSS signal at anytime since there is no other timing in the system which is currentlyvalid.

As an alternative to the above FIG. 3 embodiment in which there was onecomponent carrier for the unlicensed band which was divided intomultiple channels (seven channels in the FIG. 3 example), in anotherembodiment there is a separate component carrier allocated for eachunlicensed band data channel. This alleviates the strong requirement inthe embodiment immediately above that all transmissions be synchronizedat the symbol level, since this embodiment allows unsynchronizedtransmissions on each separate channel and so only the feedback and thedata transmissions by different devices need to be in synchronization atthe symbol level. In this per-channel component carrier embodiment,there may be one channel in the license-exempt band fully allocated forPSS signal transmissions, and this common channel 302 may itself beunsynchronized. This approach further enables random access types ofcommunication on the license exempt bands for channel access contention,conceptually similar to the random access concept in LTE and thecontention window procedures in WLAN.

One technical effect of certain embodiments of these teachings is thatthey enable a combined synchronization, resource allocation and feedbackchannelization method which does not require an explicit control channeland/or control signaling for indicating the resources for datatransmission and feedback. Another advantage is that the transmitter ofthe data can scale the resource utilization based on the need andavailability, and perform synchronization at the same time. Theseteachings enable ad hoc networking, which is an evolving path for theLTE and LTE-A systems as well as other RATs, and could be utilized forclustered device-to-device communications.

Now are detailed with reference to FIG. 4 further particular exemplaryembodiments from the perspective of the portable communicating device.FIG. 3 may be performed by the whole first or second device 20, 24 shownat FIG. 5, or by one or several components thereof such as a modem. Atblock 402 the device 20, 24 maps a feedback radio resource 310-0 in alicense-exempt frequency band from a data radio resource 306-0 to atleast one frequency sub-band which the data radio resource excludes, andspaced in time from the data radio resource by a predetermined interval308. At block 404 the second device sends, and/or the first devicereceives, feedback for information received (by the second device) orsent (by the first device) on the data radio resource on the mappedfeedback radio resource.

Further portions of FIG. 4 represent various of the specific butnon-limiting embodiments detailed above. At block 406 the at least onefrequency sub-band comprises frequency edges of a radio channel bearingthe data radio resource. The alternative to this is at block 408, wherethe at least one frequency sub-band comprises frequency edges of acomponent carrier bandwidth in which lies a radio channel bearing thedata radio resource. As noted above but not summarized at FIG. 4, thefeedback can be an acknowledgement or a negative acknowledgement; andthe predetermined interval 308 is a function of a size of theinformation within the data radio resource.

A further embodiment is shown at block 410 of FIG. 4 from theperspective of the first device 20, namely the first device 20 delayssending the information on the data radio resource until a predeterminedtime offset 330 following an end time of a previous transmission on theradio channel, in which the predetermined time offset comprises aninteger multiple of a symbol time. The embodiment for which the firstdevice does not know the end time for a previous transmission on theradio channel is summarized at block 412, in which the first device 20delays sending the information on the data radio resource until apredetermined time lapse which comprises the predetermined interval 308plus a fixed length 309 of the feedback radio resource.

Block 414 is from the perspective also of the first device 20 andsummarizes synchronization in the system. There the first device 20receives a synchronization signal (prior to 304 on channel 302 in FIG.3) on a common channel 302 and synchronizes the data radio resource310-0 to timing defined by the synchronization signal only if asynchronization timer in the first device 20 has not expired. Andfinally, not specifically shown at FIG. 4 but detailed above asfollowing from the synchronization at block 414, the first device 20re-transmits the synchronization signal 304 on the common channel 302after an integer multiple of symbol time has elapsed following receptionof the synchronization signal. In this case the same synchronizationsignal may be transmitted but with a different cyclic shift to map tothe data radio resource according to one non-limiting embodiment.

FIG. 4 is a logic flow diagram which may be considered to illustrate theoperation of a method, and a result of execution of a computer programstored in a computer readable memory, and a specific manner in whichcomponents of an electronic device are configured to cause thatelectronic device to operate. The various blocks shown in FIG. 4 mayalso be considered as a plurality of coupled logic circuit elementsconstructed to carry out the associated function(s), or specific resultof strings of computer program code stored in a memory.

Such blocks and the functions they represent are non-limiting examples,and may be practiced in various components such as integrated circuitchips and modules, and that the exemplary embodiments of this inventionmay be realized in an apparatus that is embodied as an integratedcircuit. The integrated circuit, or circuits, may comprise circuitry (aswell as possibly firmware) for embodying at least one or more of a dataprocessor or data processors, a digital signal processor or processors,baseband circuitry and radio frequency circuitry that are configurableso as to operate in accordance with the exemplary embodiments of thisinvention.

Reference is now made to FIG. 5 for illustrating a simplified blockdiagram of various electronic devices and apparatus that are suitablefor use in practicing the exemplary embodiments of this invention. InFIG. 5 there is a first device 20 operating in the licensed band in theLTE system under an eNB 22 via wireless link 21, and there is also asecond device 24 operating in another licensed band in the UTRAN systemunder a Node B 26 via wireless link 25. Not shown are higher networknodes for the LTE and UTRAN systems which provide connectivity withfurther networks such as for example a publicly switched telephonenetwork PSTN and/or a data communications network/Internet. There mayalso be a data and/or control path (not shown) coupling the Node B 26with the eNB 22.

The first device 20 includes processing means such as at least one dataprocessor (DP) 20A, storing means such as at least one computer-readablememory (MEM) 20B storing at least one computer program (PROG) 20C,communicating means such as a transmitter TX 20D and a receiver RX 20Efor bidirectional wireless communications with the eNB 22 and with thesecond device 26 via one or more antennas 20F. While only onetransmitter and receiver are shown it is understood there may be morethan one. Inherent in the first device is also a clock from whichvarious software-defined timers are run, such as for example thesynchronization timer mentioned above. Also stored in the MEM 20B atreference number 20G is the feedback mapping rules and implementingalgorithm so the first device can map from a data radio resource to afeedback radio resource as detailed above for the various embodiments.The second device 24 is functionally similar with blocks 24A, 24B, 24C,24D, 24E, 24F and 24G. the first and second devices 20, 24 communicatewith one another directly according to the various described embodimentsusing the direct wireless link 23.

The eNB 22, or more generally the network serving cell, also includesprocessing means such as at least one data processor (DP) 22A, storingmeans such as at least one computer-readable memory (MEM) 22B storing atleast one computer program (PROG) 22C, and communicating means such as atransmitter TX 22D and a receiver RX 22E for bidirectional wirelesscommunications with the UE 20 via one or more antennas 22F. In someembodiments the first device learns of open channels in thelicense-exempt band from the eNB 22, which stores this information itgleaned from the whitespace database in its memory at 22G. The Node B 26is functionally similar with blocks 26A, 26B, 26C, 26D, 26E, 26F and26G.

While not particularly illustrated for the devices 20, 24 or the networkaccess nodes 22, 26, those apparatus are also assumed to include as partof their wireless communicating means a modem which may be inbuilt on anRF front end chip within those devices 20, 22, 24, 26 and which alsocarries the TX 20D/22D/24D/26D and the RX 20E/22E/24E/26E.

At least one of the PROGs 20C/24C in the first and second devices 20, 24is assumed to include program instructions that, when executed by theassociated DP 20A/24A, enable the device to operate in accordance withthe exemplary embodiments of this invention, as was discussed above indetail. The network access nodes 22, 26 may also have software toimplement certain aspects of these teachings such as providinginformation about available license-exempt bands as detailed above. Inthese regards the exemplary embodiments of this invention may beimplemented at least in part by computer software stored on the MEM 20B,22B, 24B, 26B which is executable by the DP 20A/24A of the communicatingdevices 20, 24 and/or by the DP 22A/26A of the network access nodes 22,26; or by hardware, or by a combination of tangibly stored software andhardware (and tangibly stored firmware). Electronic devices implementingthese aspects of the invention need not be the entire apparatus 20, 22,24, 26 as shown, but exemplary embodiments may be implemented by one ormore components of same such as the above described tangibly storedsoftware, hardware, firmware and DP, or a system on a chip SOC or anapplication specific integrated circuit ASIC or a digital signalprocessor DSP.

In general, the various embodiments of the first and/or second device20, 24 can include, but are not limited to: data cards, USB dongles,user equipments, cellular telephones; personal portable digital deviceshaving wireless communication capabilities including but not limited tolaptop/palmtop/tablet computers, digital cameras and music devices,Internet appliances, remotely operated robotic devices ormachine-to-machine communication devices.

Various embodiments of the computer readable MEMs 20B/22B/24B/26Binclude any data storage technology type which is suitable to the localtechnical environment, including but not limited to semiconductor basedmemory devices, magnetic memory devices and systems, optical memorydevices and systems, fixed memory, removable memory, disc memory, flashmemory, DRAM, SRAM, EEPROM and the like. Various embodiments of the DPs20A/22A/24A/26A include but are not limited to general purposecomputers, special purpose computers, microprocessors, digital signalprocessors (DSPs) and multi-core processors.

Various modifications and adaptations to the foregoing exemplaryembodiments of this invention may become apparent to those skilled inthe relevant arts in view of the foregoing description. While theexemplary embodiments have been described above in the context of theE-UTRAN (LTE/LTE-A) system, it should be appreciated that the exemplaryembodiments of this invention are not limited for use with only this oneparticular type of wireless communication system, and that they may beused to advantage in other wireless communication systems such as forexample GERAN, UTRAN and others which facilitate direct communicationsby user or other portable radio devices over license-exempt spectrum.

Some of the various features of the above non-limiting embodiments maybe used to advantage without the corresponding use of other describedfeatures. The foregoing description should therefore be considered asmerely illustrative of the principles, teachings and exemplaryembodiments of this invention, and not in limitation thereof.

1. An apparatus comprising: at least one processor and at least onememory storing a computer program; in which the at least one memory withthe computer program is configured with the at least one processor tocause the apparatus to at least: map a feedback radio resource in alicense-exempt frequency band from a data radio resource to at least onefrequency sub-band which the data radio resource excludes and spaced intime from the data radio resource by a predetermined interval; and sendor receive feedback for information received or sent on the data radioresource on the mapped feedback radio resource.
 2. The apparatusaccording to claim 1, in which the at least one frequency sub-bandcomprises frequency edges of a radio channel bearing the data radioresource.
 3. The apparatus according to claim 1, in which the at leastone frequency sub-band comprises frequency edges of a component carrierbandwidth in which lies a radio channel bearing the data radio resource.4. The apparatus according to claim 1, in which the feedback comprisesan acknowledgement or a negative acknowledgement.
 5. The apparatusaccording to claim 1, in which the predetermined interval is a functionof a size of the information within the data radio resource.
 6. Theapparatus according to claim 1, in which the at least one memory withthe computer program is configured with the at least one processor tocause the apparatus to receive the feedback after sending theinformation on the data radio resource, and to delay sending theinformation on the data radio resource until a predetermined time offsetfollowing an end time of a previous transmission on the radio channel,in which the predetermined time offset comprises an integer multiple ofa symbol time.
 7. The apparatus according to claim 1, in which the atleast one memory with the computer program is configured with the atleast one processor to cause the apparatus to receive the feedback aftersending the information on the data radio resource, and to delay sendingthe information on the data radio resource until a predetermined timelapse for the case the apparatus is not aware of an end time for aprevious transmission on the radio channel, in which the predeterminedtime lapse comprises the predetermined interval plus a fixed length ofthe feedback radio resource.
 8. The apparatus according to claim 1, inwhich the at least one memory with the computer program is configuredwith the at least one processor to cause the apparatus further toreceive a synchronization signal on a common channel and synchronize thedata radio resource to timing defined by the synchronization signal onlyif a synchronization timer has not expired.
 9. The apparatus accordingto claim 8, in which the at least one memory with the computer programis configured with the at least one processor to cause the apparatusfurther to re-transmit the synchronization signal on the common channelafter an integer multiple of symbol time has elapsed following receptionof the synchronization signal.
 10. A method comprising: mapping afeedback radio resource in a license-exempt frequency band from a dataradio resource to at least one frequency sub-band which the data radioresource excludes and spaced in time from the data radio resource by apredetermined interval; and sending or receiving feedback forinformation received or sent on the data radio resource on the mappedfeedback radio resource.
 11. The method according to claim 10, in whichthe at least one frequency sub-band comprises frequency edges of a radiochannel bearing the data radio resource.
 12. The method according toclaim 10, in which the at least one frequency sub-band comprisesfrequency edges of a component carrier bandwidth in which lies a radiochannel bearing the data radio resource.
 13. The method according toclaim 10, in which the feedback comprises an acknowledgement or anegative acknowledgement.
 14. The method according to claim 10, in whichthe predetermined interval is a function of a size of the informationwithin the data radio resource.
 15. The method according to claim 10, inwhich the method comprises receiving the feedback after sending theinformation on the data radio resource; the method further comprisingdelaying sending the information on the data radio resource until apredetermined time offset following an end time of a previoustransmission on the radio channel, in which the predetermined timeoffset comprises an integer multiple of a symbol time.
 16. The methodaccording to claim 10, in which the method comprises receiving thefeedback after sending the information on the data radio resource; themethod further comprising delaying sending the information on the dataradio resource until a predetermined time lapse for the case an end timefor a previous transmission on the radio channel is unknown, in whichthe predetermined time lapse comprises the predetermined interval plus afixed length of the feedback radio resource.
 17. The method according toclaim 10, the method further comprising: receiving a synchronizationsignal on a common channel and synchronizing the data radio resource totiming defined by the synchronization signal only if a synchronizationtimer has not expired.
 18. The method according to claim 17, the methodfurther comprising: re-transmitting the synchronization signal on thecommon channel after an integer multiple of symbol time has elapsedfollowing reception of the synchronization signal.
 19. A computerreadable memory tangibly storing a computer program executable by atleast one processor, the computer program comprising: code for mapping afeedback radio resource in a license-exempt frequency band from a dataradio resource to at least one frequency sub-band which the data radioresource excludes and spaced in time from the data radio resource by apredetermined interval; and code for sending or receiving feedback forinformation received or sent on the data radio resource on the mappedfeedback radio resource.
 20. The computer readable memory according toclaim 19, in which the at least one frequency sub-band comprisesfrequency edges of a radio channel bearing the data radio resource. 21.(canceled)
 22. (canceled)
 23. (canceled)
 24. (canceled)
 25. (canceled)26. (canceled)
 27. (canceled)